Additive Manufacturing is a process that creates physical parts from a three-dimensional digital file. The current most common additive manufacturing techniques include stereo lithography (SLA) and selective laser sintering (SLS). These processes build a three-dimensional part by converting the digital file into several horizontal layers. For the sake of clarity, this application refers to each layer of an additive manufactured part created by SLA or SLS as a slice. The base slice is created, and then successive slices are added one at a time on top of each other, building the part from the bottom up.
SLA performs this method by extruding liquid resin, which is curable with a UV laser. The resin is extruded first in the base slice, and then a UV light cures and solidifies the slice. Another slice is extruded atop that slice, and cured. This process continues adding slices upon each other until the part is complete.
SLS uses a reductive technique. A layer of small particles, comparable to powder or sand, is placed on a printing surface. The particles may be plastic, metal, glass, or other material. A laser draws the first slice of the part in the particles, fusing them together to form the base of the part. Another layer of particles are then added across the entire printing surface. The laser then fuses the newly added particles together in the desired shape of the next slice. More particles are added, and the laser fuses more slices until the entire part is fused. The part is then removed from the loose particles.
Additionally there are other additive manufacturing techniques similar to SLS that use a binder material, instead of a laser, to fuse particles together. It still builds the part with a slicing technique, starting from the base and adding slices one at a time.
To strengthen the parts, some additive manufacturing techniques add reinforcing particles. This creates a heterogeneous mixture rather than pure resin, plastic, or metal. The reinforcing particles are randomly distributed throughout the part. A comparable application is the addition of aggregate to cement to create concrete.
The additive manufacturing techniques described above have several disadvantages. The process of building parts layer by layer is slow, and necessitates parts being designed to accommodate the slicing process. The parts are built slice upon slice, with vulnerable joints between each, creating a relatively weak part. Additionally, the materials used are mostly homogeneous plastic or resin, with a minority of manufacturers adding reinforcing particles. These materials have much room for improvement with regard to strength and efficiency.
There is a need for a method and apparatus of additive manufacturing that builds parts faster and easier than the current slicing methods, and also creates stronger parts than the current single or composite materials in use.